Wireless sensors are known. Such devices typically comprise an integral device having one or more sensors (to sense any of a wide variety of conditions and parameters) and a transmitter or transceiver to support wireless telemetry of sensor data. Many such devices further include a portable power supply (such as a battery pack and/or a solar cell array) and/or control logic to facilitate various actions and responses.
Networks of such wireless sensors have also been proposed. Proliferation of corresponding system designs has occurred as various enabling technologies (such as microelectromechanical system (MEMS) design to facilitate the provision of very small, accurate, cost effective, and low power sensor mechanisms) have become available. Pursuant to one deployment scheme, a plurality of wireless sensors are strewn over a geographic area of interest (such as, for example, a farm or ranch). These sensors then communicate with one another pursuant to a pre-arranged or self-organized communication protocol and schedule. In many such proposals, the wireless sensors communicate in this fashion pursuant to a relatively fixed or otherwise predictable schedule. So configured, the wireless sensors are then able to assume a so-called sleep mode during intervening periods in order to conserve power.
In many wireless sensor networks, one or more collection points serve to receive the sensor data as generated by the various wireless sensors that comprise the network. For a variety of reasons, however, such collection points are often not able to receive such information directly from each wireless platform (for example, the collection point may be located beyond the transmission range of a given wireless sensor). One useful proposal suggests relaying data from one wireless sensor to another as needed in order to transport sensor data from a given source to a desired endpoint. In a relatively simple configuration, such an approach may prove acceptable.
There are other circumstances where such an approach remains insufficient, however. In some systems, groups of wireless sensors are organized into clusters (such clusters may be differentiated by range, purpose, wireless communications protocol and/or modulation, or any number of other causes or criteria). Relaying data from one cluster to a collection point via another cluster can be accomplished using so-called bridge nodes (these being wireless sensors that are able to function compatibly in both clusters), but such an approach gives rise to a new set of problems. In particular, the communications duty cycle of such a bridge node will typically at least double as compared to the wireless sensors that otherwise comprise these clusters. This occurs because the bridge node becomes active during the communication cycles of both clusters that it serves to link. As a result, the bridge nodes will deplete their portable power source more rapidly than other platforms within these clusters and therefore fail sooner. When this occurs, the link between the clusters breaks and the collection point no longer has access to data still being collected by the now-stranded cluster of wireless sensors.
One simple solution would be to provide the bridge nodes with a larger portable source. Such an approach, however, dictates that some wireless platforms within a given deployment are different than others. This can raise costs significantly, both to provide and supply a plurality of platforms and to ensure that each type of sensor is deployed properly (that is, to ensure that bridge nodes are positioned where they can, in fact, usefully serve as a bridge node). Problems such as these tend to militate against the use of such a solution.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are typically not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.